1. Field of the Invention
This invention relates generally to closures for containers, and more particularly to a closure which seals a rim of an open mouth of a container at a plurality of discrete locations along the surface of the rim and container mouth where each location provides a seal over a significant portion of the surface of the container and stabilizes both the interior and exterior surfaces of the container mouth from distortion during and after installation of the closure.
2. Description of the Related Art
Closures or caps for containers typically are of the threaded screw or snap type construction and are utilized to close the mouth of the container in either a resealable or non-resealable manner. Manufacturers of products which utilize such closures typically require a closure to perform under several conditions or specifications which vary from product to product and between manufacturers.
One condition or specification is that a closure be capable of being applied to a container when the container and/or the contents therein still are hot or where the container and contents are heated after application of the closure. In such a situation, temperatures of the contents can exceed 150.degree. which can distort the container mouth from its circular shape. Accordingly, closures utilized in such applications must not only ensure proper sealing about the container mouth or rim, but must assist in maintaining the circular shape of the container mouth during and after application of the closure.
Furthermore, containers frequently are sealed with a closure where a vacuum is provided within the container. Thus, these types of closures initially must seal the container against an inward pressure force provided by the vacuum. After opening, the same closure must then seal the container against an outward pressure force which can be provided by the weight of the container contents themselves as well as any gas pressure which may be generated by the contents, such as gas pressure provided by a carbonated beverage.
To provide a leak-proof seal about the rim of the container mouth, closures can include separate liners or be molded to include one or more rim engagement member that resists leakage of the container contents. Separate liners typically are attached to the inside closed end of the closure and can require increased manufacturing costs to insert and secure the liner to the closure and/or modify the closure to accept the liner.
An example of a closure having a molded rim engagement member is shown in U.S. Pat. No. 4,122,965 which includes one non-flexing sealing fin which projects downwardly from the closed end of the closure to engage the container rim proximate the center of the width of the rim. Such a sealing fin, however, only provides contact with the center of the rim along a single engagement line which may not provide an adequate seal, especially with container contents under pressure. Additionally, the sealing fin is crushed and deformed during installation which can restrict proper resealing of the closure upon reinstallation on the container.
U.S. Pat. No. 4,220,250 similarly discloses a closure having one sealing ring extending from an internal surface of a closure whose flexing is limited by an additional support ring depending from the closed end of the closure and which provides enhanced sealing with increased pressure within the container. A bead also is included on the internal surface of the closure side wall for locating and centering of the closure as it is finally tightened on the container. As with the closure described above, sealing is provided by a bead formed on the sealing ring that only provides contact with the center of the rim along a single engagement line. Additionally, an initial vacuum within the container may cause the structure that provides the enhanced sealing to open and enable the contents to leak out.
U.S. Pat. No. 4,360,114 discloses a closure having two resilient concentric sealing rings depending from the top portion of the cap where the outer sealing ring is longer. Both rings, however, contact the central portion of a tapered container rim and flex outward which can cause leakage from outward pressure within the container causing outward flexing of the rings.
It therefore is desirable to provide a closure which can seal a container rim, even when the container and/or contents are subjected to heat or where excess pressure or a vacuum is provided within the container, where the closure engages the container rim and mouth in a plurality of locations and provides sealing over a significant portion of the surface area of the container and which stabilizes both the interior and exterior surfaces of the container from distortion during and after installation of the closure.